Cut-out



1933- 4 J. A. M. VAN LIEMPT 1,934,457

CUT-OUT Filed Sept. 3, 1951 fi 7 Fi gG JUHANNEE All. VAAZ'LIEMPT m a zwmw.

I-L's AT Tammy Patented Nov. 7, 1933 UNITED'STATES CUT-OUT Johannes Antonius Maria van Liempt, Eindhoven, Netherlands, assignor to General Electric Company, a corporation of New York Application September 3, 1931, Serial No. 561,045, and in the Netherlands September 12, 1930 4 Claims. (01. 200-118 I My invention relatesto electric short-circuiting or cutout devices and more particularly to such devices used in a series circuit. Still more particularly my invention relates to short-circuiting or cutout devices comprised in electric lamps or similar devices for cutting out a particular device upon failure thereof. These lamps are used for such purposes as street lighting, railway lighting and Christmas tree lighting. The cutout material, which is disposed across the lead wires or other parts of the circuit so as to be in parallel with the filament, conducts no current or substantially no currrent at the operating voltage of the lamp but when the filament burns out, the entire se ries voltage is applied across said cutout which then becomes conducting and maintains the circuit through the remaining lamps of the series. Powdered materials such as Fe3O4, PbS, FeS, and powdered metals have been suggested as materials for such a cutout. The breakdown voltage of such powders depends upon the compactness with which they are placed in the stem tube of the lamp. This compactness is subject to variations under vibration which cause the value or" the breakdown voltage to vary. The powders are also sensitive to theadsorption of vapors which affect the value of the breakdown voltage and since some vapor isalways formed when the lamps are cemented it is difficult to control that voltage. If the lamps containing such powders are used in a direct current circuit, it has been shown that said powders may become conducting after a certain time with the result that the breakdown voltage is affected and the filament does not receive sufficient current. Still another disadvantage of said powders is the difiiculty of obtaining constant values of breakdown voltage between 20 and 100 volts.

It has also been suggested to use a small strip provided with a coating of A1203 as a cutout, said coating to be normally insulating'but to be punctured by an excessive voltage. In this case it is also difficult to obtain a breakdown voltage of less thanllO voltssinoe the layer of A1203 'must be so thin that a small difference in the thickness of the layer will greatly affect the value of the breakdown voltage. It will also be mechanically weak.

It has been shown that the present invention does away with the hereinbefore mentioned disadvantages. Other features and advantages of my invention will appear from the following description of species thereof.

According to my invention, the cutout material is a tungsten bronze such as NazwzOs, NazWsOa, NasWsO a, etc. The value of the breakdown voltage depends upon the thickness of the layer, upon the alkali or alkalin earth metal comprised by the bronze, and upon the type of bronze. The thickness of the bronze layer to beused at low voltages is quite considerable so that a slight difference in thickness does not appreciably affect the breakdown voltage. According to my invention the bronze layer may be provided on a conductor which is placed across the lead-in wires or the layer may be provided on one or both of the lead-in wires with the conductor making contact with said layers. The cutout may be located within the bulb or outside of it.

I To obtain a tungsten bronze layer, a tungsten wire or strip may be drawn through a fused acid tungstate. This forms a yellow bronze and the reaction which takes place is very probably represented by the equation By another method the tungsten Wire or strip is used as the cathode during the electrolysis of a fused acid tungstate. This reaction may be represented by the formula These two methods may be combined. If necessary the salts that have not been converted may be reduced to bronze with hydrogen. It is also possible to coat a wire or strip with an acid tungstate and reduce it later to a bronze with hydrogen. This method and the method of elec trolysis hereinbefore mentioned may be applied to a wire or strip consisting of copper, nickel or nection as shown in Fig. 5; Fig. 6 is a side view of a cutout strip; Fig. 7 is a front View thereof;

Fig. 8 is a front elevation of an Edison socket;

Fig. 9 is a bottom view of said socket; and Fig. 10 is a fragmentary View of said socket at right angles to Fig. 9.

Referring to Fig. 1, the lamp comprises a bulb 10, filament 11, mounted on inner leads 1213, the ends of which are sealed into a stem press 14, and outer leads 15l6, the ends of which are also sealed into the stem press 14. The cutout comprises a copper strip 17 provided with a layer of bronze 18 which may be connected across the leads 15-16 with the bronze layer 18 ad jacent to said lead wires as in Fig. 2, or with the bronze layer adjacent to one lead wire 15 and the copper strip 17 adjacent to the other lead wire 16 as in Fig. 3. In case of an excessive volt age due to the failure of the filament 11, the bronze layer 18 would break down and allow the copper strip 17 to short circuit the lamp.

The lamp in Fig. 4 comprises a bulb 19, base 20, filament 21 mounted on inner leads 222.3, the ends of which are sealed in a stem press 24, and outer leads 2526, the ends of which are also sealed in the stem press 24. The lead wire 26 is provided with a layer of bronze 27. A nickel strip 28 (Fig. 5) is placed across the leads 25--26 so as to make contact with the lead wire 25 and the bronze coating 27 on the lead wire 26. The lead wire 26 may be of tungsten, copper or nickel. In place of the tungsten a more flexible wire may be made by coating a molybdenum wire with tungsten.

The cutout shown in Figs. 6 and '7 is formed of a copper strip 29 provided on both sides with bronze coatings 30. Said cutout is placed between S clamps 31 and 32 (Figs. 8, 9, and 10) connected to side and center terminals 33 and 34 respectively of an Edison socket comprising a screw shell 35 and support 36. i

For breakdown voltages between 20 and 100 volts on either direct or alternating current, the so-called blue tungsten bronze of the probable composition NazW3O9 of a thickness of between and microns has been found especially effective. In general, the value of the breakdown voltage increases with the acidity of the bronze and with the thickness of the layer of bronze.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A cutout or electric short circuiting device comprising a bronze of a refractory metal.

2. A cutout or electric short-circuiting device comprising a tungsten bronze.

3. A cutout or electric short-circuiting device comprising a metal coated with a bronze of a refractory metal.

4. A cutout or electric short-circuiting device comprising tungsten coated with a tungsten bronze.

J OHANNES ANTONIUS MARIA VAN LIEMPT. 

